The risk for suicide is a major health concern for lesbian, gay, bisexual, and transgender (LGBT) youth. We propose a longitudinal study to recruit and follow a diverse sample of 1160 LGBT youth aged 15 to 21 youth from community-based organizations in three metropolitan areas across the United States. We will use snowball and respondent-driven sampling to increase the number and diversity of the participants. The youth will be assessed four times, post baseline, over a three-year period. These assessments will allow us to determine changes in constellations, magnitudes, and developmental sequences of risk and protective factors for suicidal behaviors with a particular emphasis on the major components of the interpersonal psychological theory of suicide: thwarted belongingness, perceived burdensomeness, and the capacity for self-lethal injury. We will simultaneously document whether or not risk and protective factors for suicide are uniquely related to LGBT youths'developmental milestones. Our emphasis will be comparing LGBT youth who do and do not experience any suicidal behaviors, i.e., ideation, threats, and serious attempts. Documenting the protective factors of the youth who emerge with positive psychological adjustment is crucial to the generation of knowledge of those youth whose adjustment is compromised by LGBT-related experiences emanating from society's negative view of youth who do not conform to sexual and gender role expectations. The knowledge we generate will allow us to more accurately assess LGBT youth at risk for suicidal behaviors, identify those risk factors that are malleable to change at various developmental milestones, and to create preventive messaging and intervention models that simultaneously increase protective factors and reduce risk factors. PUBLIC HEALTH RELEVANCE: Studies have repeatedly found higher rates of suicidal behaviors among lesbian, gay, bisexual, and transgender (LGBT) youth than their heterosexual peers. Recent studies have also found that compared to prior cohorts, contemporary LGBT youth are increasingly aware of, identifying and disclosing their sexual and gender identities earlier in their developmental trajectories;these factors have been related to suicidal risk factors such as bullying, harassment, marginalization, and victimization by family members and peers. As society has not been able to change the negative experiences that lead to suicidal behaviors among some LGBT youth, we need to provide public and mental health workers with evidenced-based research so that they can identify and enhance protective factors while simultaneously reducing malleable risk factors for suicidal behaviors when working with LGBT youth.